Speaker
Description
The study of the Collins asymmetry in $p^{\uparrow}p$ collisions provides a crucial experimental probe for quark transversities and polarized transverse-momentum-dependent (TMD) fragmentation functions.
In this talk, we present high-precision measurements of the Collins asymmetry for $\pi^{\pm}$ within jets from transversely polarized ${p^{\uparrow}p}$ collisions at $\sqrt{s}$ = 510 GeV by using the STAR detector.
In terms of an energy-scaled jet transverse momentum ratio, $x_{\mathrm{T}} = 2p_{\mathrm{T,jet}}/\sqrt s$, a remarkable consistency is observed for Collins asymmetry of $\pi^{\pm}$ between $\sqrt{s}$ = 200 GeV and 510 GeV. This indicates that the Collins asymmetry is nearly energy independent, with at most a mild scale dependence, in $p^{\uparrow}p$ collisions.
The experimental results are compared to theoretical calculations, including models with and without TMD evolution.
Thus, these results enable unique tests of evolution and universality in the TMD formalism, providing important constraints for the transversity distributions and the Collins fragmentation functions.
